Computable translucency as a function of thickness in a multi-layered zirconia.

STATEMENT OF PROBLEM: Determining the relationship between variable thicknesses and the translucency of dental ceramics is essential for optimizing esthetics in different clinical situations. PURPOSE: The purpose of this in vitro study was to analyze the relationship between layer thickness and translucency of 2 multi-layered monolithic zirconia materials and to develop an equation by which the grade of translucency can be calculated dependent on the materials' layer thicknesses in advance. MATERIAL AND METHODS: Two semisintered multi-layered zirconia blanks, namely KATANA Zirconia Super Translucent Multi-Layered Disk (Noritake Dental Supply Co, Ltd) and Zirconia Ultra Translucent Multi-Layered Disk (UTML) (Noritake Dental Supply Co, Ltd), were sectioned (N=96) to separate the 4 layers (n=12 per layer): enamel layer, transition layer 1, transition layer 2, body layer. All specimens were sintered in a furnace (M2 Plus; Thermo-Star) at 1500°C for 2 hours and automatically polished under water cooling up to P2400 for the thicknesses of 1.6, 1.3, 1.0, 0.7, and 0.4 mm. Transmittance of visible light was measured using a spectrophotometer (Lambda 35; Perkin Elmer). Data were analyzed using the Kolmogorov-Smirnov, 2-way ANOVA, and Scheffé post hoc tests (α=.01) and curve fitting. RESULTS: Analyzing the fitting of the values of the 8 material groups to the linear, exponential, and logarithmic curves, 7 of the 8 groups (not UTML body layer) fitted the most (R-square value closer to 1.0) to the logarithmic curve. Constants were obtained from the distance to the x-axis and the curvature. CONCLUSIONS: The methodology of this study provided the materials' specific constants a and b by analyzing the translucency behavior of KATANA Super Translucent Multi-Layered Disk and Ultra Translucent Multi-Layered Disk in different thicknesses, allowing further translucency calculation by applying the developed formula and the constants.

Multidisciplinary full-mouth rehabilitation with soft tissue regeneration in the esthetic zone.

OBJECTIVE: Oral rehabilitation often requires a multidisciplinary approach including restorative dentistry, prosthodontics, and periodontology to fulfill high esthetic and functional demands, frequently combined with changes in the vertical dimension. The presence of gingival recessions can be associated with numerous factors, such as brushing or preparation trauma and persistent inflammation of the gingiva due to inadequate marginal fit of restorations. Because gingival recessions can cause major esthetic and functional problems, obtaining stability of the gingival tissue around prosthetic restorations is of essential concern. Modifications of the occlusal vertical dimension require sufficient experience of the whole dental team. Especially in patients with functional problems and craniomandibular dysfunction, a newly defined occlusal position should be adequately tested and possibly adjusted. CLINICAL CONSIDERATIONS: This case report presents a complete prosthetic rehabilitation combined with a periodontal surgical approach for a patient with gingival recessions and functional/esthetic related problems. The vertical dimension was carefully defined through long-term polymethyl methacrylate provisionals as a communication tool between all parts involved. All-ceramic crowns were inserted after periodontal healing as definitive rehabilitation. CONCLUSIONS: Complex rehabilitation in patients with high esthetic demands including soft tissue corrections requires a multidisciplinary team approach that consists of periodontal surgeon, dentist and dental technician.